Rotating URLs?

Hey guys, quick tech question... I have a landing page the redirects to an offer.

Let's say I want to test 2 offers, how do I put in code to split the traffic randomly between 2 offers/URLs?

Right now my "thank you" page redirects to 1 offer. I want it to randomly split traffic between 2 offers?

How?

Thanks bros!

Here's one of the best articles I know of on this topic:

http://www.smartpassiveincome.com/h...ts-using-google-optimizer-for-better-results/